In this paper, two broadband measurement methods, shorted microstrip method and microstrip trnasmission method, are discussed, and the complex permeability of ferromagnetic thin films is measured from 100MHz to 18GHz. The S-parameters of the two measurement fixtures are measured by vector network analyzer (VNA). The perturbations of the thin film loaded in the measurement fixture are analyzed; the discontinuity between coaxial and microstrip is considered; the effective permeability is deduced from measured S-parameters; the permeability of ferromagnetic thin films is extracted from effective permeability by using conformal mapping. The results show that the experimental results agree with the theoretical ones closely, and higher measurement sensitivity and accuracy are achieved by using shorted microstrip method.
In this paper, a novel microstrip bandstop filter by etching a square split ring in the center of microstrip line is proposed. Low insertion loss in the passband, high rejection level and integrated structure should be mentioned as advantages for this resonator. A transmission line model for this resonator is introduced and its resonant frequency is calculated analytically. Good agreement between the experimental results, full-wave simulation, transmission line model and analytical result has been achieved.
We report on the modeling of light reflection in disordered chirped mirrors with a photonic band gap in the visible. The stop band limits have a threshold-like behavior as a function of disorder and sustain a certain amount of disorder before changing. We determine the disorder value that leads to a substantial broadening of the total reflection range.
This work presents a novel design for high-impedance surface (HIS) embedded dielectric resonator (DR) structures to efficiently control bandwidth of suppressing simultaneous switching noise (SSN) in high speed digital printed circuit boards (PCBs). The proposed structure is designed by periodically embedding high dielectric constant materials into the substrate between a continuous power plane and a middle patch. A conventional HIS structure has only one resonance frequency to produce stopband while the proposed structure has two resonances to widen the suppression bandwidth. The -30 dB stopband of the proposed structure is about two times wider than that of a conventional HIS structure. The excellent SSN suppression behavior was verified by measurements and simulations.
Strong visible green upconversion emission in nanocrystalline BaZrO3:Yb3+ powder, obtained by a hydrothermal process at 100ºC, is reported. The unconverted emission has a quadratic dependence on the pump intensity with a lifetime around half that of the NIR lifetime. Results suggest cooperative upconversion as the mechanism responsible for the green fluorescence. This efficient Yb3+-based cooperative up-conversion process allows the development of novel emitting materials in the UV-VIS range.
This paper demonstrates a novel way to enhance the temperature sensitivity in one-dimensional (1D) photonic band gap (PBG) material by using a ternary periodic structure (i.e. three material layers constituting a period of lattice). The temperature sensitive wavelength band shift of (Si/SiO2) periodic structure was significantly enhanced when the structure was modified by sandwiching a thin layer of Bi4Ge3O12 between every two layers, constituting a period of lattice. When the thickness of sandwiched layer was increased further enhancement in temperature sensitivity was observed. These 1D ternary PBG structures can be substituted in place of 1D binary PBG for enhancing the temperature sensing performance.
In this work, we present a novel DC-bias network for multiharmonic microwave circuits based on an arbitrarily width-modulated microstrip line. The arbitrary shape of the width-modulated microstrip line is obtained by using multiple microstrip taper sections. The method is illustrated through the design of four different DC-bias networks blocking from 1 to 4 harmonic components of a 2.5 GHz signal. The designs with an optimum shape for the arbitrarily widthmodulated microstrip line have been manufactured and measured, obtaining a good agreement between the simulated and measured behavior.
A compact circularly polarized (CP) microstrip antenna with inserted nine cross slots is proposed to reduce the size and widen the beamwidth. The antenna is operated at 1.268 GHz, and built by using a substrate with a coaxial probe feed. The impedance bandwidth (VSWR < 2) is 1.5% and the 3 dB axial ratio bandwidth is 0.52%. The measure gain is 4.5 dBi and beamwidth is about 110o. The measured results for the compact CP antenna with embedded cross slots size shows that the resonate frequency is significantly lowered from 1.951 GHz to 1.268 GHz, corresponding to a 35% antenna size reduction compared with the one without any slot.
Based on a new concept, i.e., charge moment tensor and the rotational equation of a charged dielectric rigid body about a fixed-point under a uniform external magnetic field, one symmetrical case has been rigorously solved. The rotational stability has been analyzed in detail for two cases, general and symmetrical, respectively, by means of some techniques of matrix analysis.
An accurate 2D steady state mathematical model for induction heating process is described and additional results of electromagnetic field, eddy currents distribution and volumetric heat generation have been computed for a sample setup using a finite element method. For the calculations, the input voltage of induction coil is set to be 200 ν with a frequency of 10 kHz. It was shown that for the case considered here, the distribution of eddy currents density along the radius/thickness of the workpiece has a damped sinusoidal wave-shaped form.
In this paper, a coplanar waveguide fed (CPW-Fed) ultra-wideband (UWB) antenna with dual band-notched characteristics is proposed. Two symmetrical slots are etched from the ground plane to achieve the notched band at 5.5 GHz. The other notched band at 3.5 GHz is obtained by etching a split ring slot in the radiator. The simulation and measurement show that the proposed antenna achieves an impedance bandwidth of 3.1-10.6 GHz with VSWR < 2, except in the bands of 3.2-3.8 GHz and 4.8-6.2 GHz. A nearly omnidirectional radiation pattern and stable gain with variation less than 3 dB are also observed except in the two notched bands. Moreover, time-domain characteristics of the antenna are analyzed and discussed as well.
A split-band directly modulated fiber optical CATV system employing -1 side-mode injection-locked and semiconductor optical amplifier (SOA)-based optical single sideband (SSB) modulation techniques is proposed and experimentally demonstrated. For our proposed systems, it is relatively simple to implement as only one SOA is required. Excellent performances of carrier-to-noise ratio (CNR), composite second order (CSO), and composite triple beat (CTB) were achieved over a-100 km single-mode fiber (SMF) transmission.
We propose a novel UWB bandpass filter (BPF) design using the suspended stripline (SSL). The filter composes of a lowpass and a high-pass circuit, both implemented by SSL structures. A notch response structure might be implemented to the filter by embedding a resonant slotline. The quasi-lumped elements circuit models were developed to analyze these circuits' performance. Experiments were conducted, and good agreements were observed between the measurements and simulations.
Aimed at improving the radiating characteristics (pattern and polarization) and simplifying the design of feeding network, a new approach is applied and discussed. For uniformly excited planar antenna array, by rotating each element in its local coordinates and determining the rotation angles of the elements, the 3D radiating characteristic of the planar antenna array can be improved. The Differential Evolution (DE) algorithm is applied for optimizing rotation angles of the elements. Furthermore, the effects of the elements rotation are discussed in detail.
The design and performance of a stacked patch antenna for wideband and dual-frequency operation are presented in this paper. The proposed antenna consists of a three dimensional (3D) circular transition-fed patch that is excited by a coaxial probe. By introducing a regular patch and a ring patch above the 3D circular transition-fed patch, good input impedance matching has been achieved over two frequency bands. The lower band possesses an impedance bandwidth (VSWR < 2) of 22.8% (0.775 to 0.975 GHz) and a peak gain of 5.2 dBi, while the upper band has an impedance bandwidth (VSWR < 2) of 65.8% (1.425 to 2.825 GHz) and a peak gain of 7.4 dBi. Other than the wideband and dual-band operation features, this antenna also has a beam tilted downward with a broadside beam pattern on the horizontal plane. Therefore, this antenna is very suitable for the indoor base station that is required to service several wireless communication systems, included CDMA800, GSM900, 3G, PCS, UMTS, BLUETOOTH and WLAN, by a single antenna.
This paper presents a realization of composite right/left handed transmission lines using coupled microstrip lines. This structure exploits the advantages of the microstrip lines, while increases the coupling by a floating conductor at the ground plane. The performance of this composite right/left-handed line is demonstrated by both simulated and measured results, and they show good agreement. The designed line has broad bandwidth with low losses and small size. A novel dominant mode leaky wave antenna design, using the previous structure, is presented with backward to forward scanning capability.
In this paper a new planar monopole antenna is presented. The performance parameters like return loss of the single antenna as well as transmission function, group delay, and the fidelity factor of a two-antenna system are calculated. The radiator is eye-shaped, and it can be used in dipole or monopole configurations. Good ultra wide band performance is achieved. Small size, simple design requirements and good performance are among the most advantageous features of this new of planar antennas.
A novel 16-31 GHz quadruple subharmonic monolithic passive mixer with a chip dimension of 0.82×0.7 mm2 is designed and fabricated using the 0.15 μm GaAs pHEMT process. The novel configuration of the quadruple subharmonic mixer consists of a lumped frequency diplexer and a low-pass filter utilizing a pair of anti-parallel Schottky barrier diode to achieve quadruple subharmonic mixing mechanism. The lumped frequency diplexer formed with a low-pass network and a high-pass network is used to reduce the chip dimension while operating at low frequency band and to improve the isolation between the RF and LO ports with a broadband operation. The low-pass filter supports an IF frequency range from DC to 2.5 GHz. From the measured results, the mixer exhibits a 12.5-16.5 dB conversion loss, a LO-to-RF isolation better than 15 dB, a 50-59 dB high 4LO-to-RF isolation over 16-31 GHz RF bandwidth, and an input 1 dB compression power of 2 dBm.
A CPW-fed circular slot antenna with a slot on a ground conductor is presented for harmonic suppression. The antenna has a multi-band rejection characteristic where the second and higher rejection bands are integer-multiple of the first band, and this is generated by inserting single slot on a ground conductor of the antenna. Good agreement between the simulated and measured results is reported and the integer-multiple notch bands can be adjustable by changing the length of the slot on the ground plane.
When an antenna transmits a short pulse of energy such as used for ultra-wide band applications, the pulse gets distorted upon transmission. To examine the properties of pulse transmission it is helpful to analyze the system in the time domain versus the frequency domain. Presented is a spoke top antenna for transient radiation. The spokes reduce the reflection from the open end of the antenna significantly reducing the trailing pulses commonly seen in the time domain. Comparisons are made with a dipole antenna. Both analytical, modeled and experimental results are presented.